What You Need to Know About the IIFYM Diet

The If It Fits Your Macros diet is a flexible eating plan in which “no foods are off limits,” says Brittney Bearden, a registered dietitian and sports nutrition manager with Texas Health Sports Medicine in Dallas.

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The IIFYM eating regimen allows for any and all foods, “as long as the food fits your macros,” Bearden explains. Macros, or macronutrients, are the three broad groups of food that comprise the calories we eat.

The theory undergirding the IIFYM diet is that regardless of what foods you eat – whether it’s high-calorie pizza or low-calorie broiled chicken – you’ll lose weight steadily if you stay within your target weight-loss macros, says Lisa Jones, a registered dietitian based in Philadelphia.

What Are Your Macronutrient Needs?

An individual’s daily macronutrient needs vary from person to person, Bearden says. The amount of macronutrients one consumes influences the number of calories consumed. Macronutrients are counted in grams and can be viewed as percentages of total caloric intake.

It’s helpful to know how many calories are provided in each gram of each macro. A gram of carbs and a gram of protein both contain 4 calories. One gram of fat has 9 calories, says Lauren Manaker, a registered dietitian based in Charleston, South Carolina. She consults for Zhou Nutrition.

Your macronutrient needs depend on an array of factors, including:

  • Activity level.
  • Age.
  • Gender.
  • Goals.
  • Height.
  • Weight.

Calculating and Counting Macros

The IIFYM website provides a free macro calculator, which considers your target weight and a number of factors to determine the amount of macronutrients you should eat – though you have to input your email address for results. It’s straightforward to use and, in addition to taking into account the factors that determine the amount of macronutrients you need daily, takes other variables into account, says Lana Nasrallah, manager of clinical nutrition at UNC Health, a not-for-profit integrated health care system based in Chapel Hill and owned by the state of North Carolina.

Other factors the IIFYM macro calculator takes into account include:

  • Medical history.
  • Motivation level.
  • Preferred diet style.

If your goal is to drop pounds, you’d reduce your caloric intake by 5% to 15%. If you want to gain pounds, you’d increase the amount of calories you consume by those percentages.

Following the IIFYM diet, your intake of protein should be between 0.7 and 1 grams per pound of body weight, and fat consumption should be between 0.25 and 0.4 grams per pound of body weight. The rest of the calories would be from carbs.

IIFYM Foods to Incorporate

As with most weight-loss plans, many individual IIFYM diets will likely be higher in protein and fat and lower in carbs, Manaker says. She notes that the proportion of protein, fat and carbs will vary per individual, “because each person’s macro needs will be different.” So, it’s helpful to know which kinds of foods are high in each macronutrient.

Foods high in carbohydrates include:

  • Baked goods (bread, cereal, cookies, muffins and pasta).
  • Beans.
  • Fruits (including apples, bananas, mangoes and plantains).
  • Starchy vegetables (corn, sweet potatoes and winter squash).  

Foods high in protein include:

  • Beef.
  • Dairy products (cheese, milk and yogurt, for instance).
  • Eggs.
  • Fish, including shellfish.
  • Legumes.
  • Nuts.

Foods high in fats include:

  • Avocado.
  • Egg yolks.
  • Fatty fish, like salmon.
  • Full-fat dairy products (including butter, cheese, cream, whole milk and ice cream).
  • Mayonnaise.
  • Nuts and nut butters.

Examples of IIFYM Dishes

Devising examples of meals that would fit in the IIFYM regimen could be confusing, because the plan is so individualized according to a person’s height, weight, gender and other factors, Jones says. A sample meal plan a registered dietitian may devise may not be anything like what a given reader’s meals would be comprised of.

As for official IIFYM meal plans, the paid subscription service gives access to a full seven-day meal plan that updates every two weeks, and pricing varies based on the plan you choose.

The meal plans include options for various types of eating, including:

  • Vegan.
  • Vegan low-carb.
  • Vegetarian.
  • Vegetarian low-carb.
  • Standard Western.
  • Standard Western low-carb.
  • Pescatarian.
  • Pollotarian (a kind of semi-vegetarian diet in which chicken is allowed, but not red meat or pork).

“A little meal planning can go a long way,” Manaker says. “Leaning on the IIFYM guidelines provided, people can plan out their meals for the entire week.”

Upsides of the IIFYM Diet

  • If you purchase one of the IIFYM meal plans, you don’t have to think much about what foods to purchase and how to prepare them, Nasrallah says. You also don’t have to use any fitness or calorie counting apps.
  • Followers of the IIFYM diet can join a private Facebook group for peer and wellness coaching.

Downsides of the IIFYM Diet

Does the IIFYM Diet Work?

A small study published in the Journal of International Society of Sports Nutrition in 2021 found that, when it comes to weight loss, a flexible diet strategy is equally effective as a rigid eating approach among individuals who engage in resistance training. Researchers found no significant differences in protein and caloric intake between a group of participants that consumed a flexible diet and another group that adhered to a rigid eating plan that called for eating specific foods.

As with any weight-loss plan, the IIFYM diet will likely work as long as you stick with it, Jones says. “Any meal pattern that promotes a reduction in overall calories will result in weight loss, at least in the short term. In addition, higher protein diets have been shown to promote satiety, and there is some solid research that suggests higher protein, low-fat diets may provide some benefits for weight loss, as compared to standard protein, low-fat diets.”

When it comes to long-term results, however, there is no firm consensus that one type of diet pattern is better than another for long-term weight loss or maintenance. “There is no one-size-fits-all diet, and people benefit from different approaches,” she says. “IIFYM can certainly be another ‘tool’ in one’s long-term weight management strategy.”